Apparatus for obtaining wires for magnetic memories

ABSTRACT

An apparatus for the continuous fabrication and testing of a wire having a conductive core covered with a thin magnetic film, wherein the conductive core is pulled with substantially zero tension through apparatus in which a magnetic film is deposited on the core and treated, and wherein the completed wire is then pushed through apparatus in which its physical properties are measured.

0 T. United States atent [151 3,669,866 Girard et a1. June 13, 1972 54]APPARATUS FOR OBTAINING WIRES 2,580,801 1/1952 Leonard ..204/28 F R MA NI 3,189,532 6/1965 Chow et a1... r....204/28 0 G ETIC MEMOR ES 3,468,7839/1969 Avellone ..204/207 [72] Inventors: Rene Fernand Victor Girard,Grenoble;

Jacques Le Guiller Avrill b th f FOREIGN PATENTS OR APPLICATIONS 29,1056/1964 Germany ..204 207 [73] Assignee: Societe Industrielle HoneywellBull, Paris,

France Primary ExaminerF. C. Edmundson Att0rney-Lewis P. Elbinger, FredJacob and Ronald T. Reil- [22] Filed. April 1, 1970 mg [21] Appl. No.:24,635

[57] ABSTRACT [30] Foreign Application Priority Data An a aratus for thecontinuous fabrication and testing of a PP d h wire having a conductivecore covere with a t in magnetic April 3, 1969 France 4.6910210 whereinthe conductive core is pulled with Substantially [52] U S C] 204/207204/28 zero tension through apparatus in which a magnetic film is [51 15/68 c23b 5/58 deposited on the core and treated, and wherein thecompleted [58] Field of Search 204/58 206411 wire is then pushed throughapparatus in which its physical properties are measured [56] RemncesCited 11 Claims, 1 Drawing Figure UNITED STATES PATENTS 3,287,238 1H1966 Latawiec et al .2 Q4 /2 07 X P'A'TENT'EDJUH 1 3 I972 INVENTORSATTORNEY BACKGROUND OF THE INVENTION This invention relates to processesand apparatus providing for continuous fabrication of wires having aconductive core covered with a thin magnetic film and for verifying thephysical properties of the wires obtained.

To effect such process, the conductive core is unwound from a drum and,under the action of driving means, traverses first a fabricationapparatus consisting of treatment means for preparing the core forreceiving a magnetic deposit and of means for effecting such deposit andtreating the deposit, and then traverses apparatus for measuring thephysical properties of the completed wire. The treatment and depositionmeans consist generally of electrolysis tanks.

In some known arrangements, the core is pushed through the corepreparation means, the deposition and deposit treatment means, and thedevice for measuring the properties of the fabricated wire. Thesearrangements, however present the following disadvantages:

It is impossible, without danger of buckling, to utilize for suchfabrication wires having a diameter of only a few s of microns;

It is impossible to employ a long wire fabrication apparatus, therebyrequiring numerous phases of treatment;

It is difficult, on the finished wire, to test the magnetostriction(necessitating a mechanical torsion and a tension of the wire), becausemechanical stresses can not be effected at the end of such fabricationapparatus without disturbing the conditions of deposit of the magneticmaterial and of the conductive layer.

Moreover, the need to have a short fabrication apparatus, and therefore,short electrolysis tanks, requires improving the particular methods ofdeposit in order to increase the speed of deposition (higher electrolytetemperatures and stronger agitation). The control of the thickness andof the composition in the case of an alloy becomes difficult. On theother hand, this method permits the orientation of the magnetization ofthe magnetic deposit in the circumferential direction by passing currentthrough wire. Nevertheless, this method of orientation is limited due tothe heating of the wire and to the tolerable drop of potential along thewire. Thus, for a diameter of 125 microns, the orienting field islimited to about 10 oersteds, which is scarcely sufficient. Thislimitation becomes all the more important as the diameter of the wiredecreases.

In other known arrangements, the wire is pulled through the fabricationapparatus and the measuring device by imposing a mechanical tension ofsome 10s to about 100 grams. This method does not have all thedisadvantages of the preceding, but it presents others. For example, itis imperative that the deposition of the magnetic film and possibly theconductive film (at the time of treatment of the core) be free ofinternal stresses in order to prevent a degradation in time of itsproperties due to the release of these stresses. If the wire duringdeposition is subjected to an external stress of tension, the release ofthis stress when it is freed generates such stress in the deposit. Thesedepositions can be effected under internal stresses of the same senseand of the same magnitude, so that the wire emerging from the output ofthe fabrication apparatus has been compensated for, but this isdifficult to provide. Moreover, if a stabilization annealing of themagnetic deposit is effected when the wire is under mechanical tension,it produces a release of the tension due to the elevated temperature (ofthe order of 300 C.), modifying the mechanical characteristics of thewire. Therefore, it is apparent that such a process is difficult toimplement if a final product free from stresses is desired. Theselimitations are all the more important as the diameter of the wire isreduced. Finally, this process presents the same disadvantages as thepreceding process relative to the disturbances produced by themagnetostriction test.

The present invention remedies these disadvantages.

SUMMARY OF THE INVENTION In accordance with the invention, the processfor continuous fabrication of a wire having a conductive core coveredwith a thin magnetic film, wherein the conductive core is prepared forreceiving a magnetic layer, the layer is deposited and then treated forconferring on it the desired properties, after which the physicalproperties of the completed wire are measured, is characterized in thatthe core is pulled with substantially zero tension during thepreparation of the wire, the deposition and the treatment of themagnetic layer, and then pushed during the measure of its physicalproperties.

For this purpose, in accordance with the invention, an arrangement forthe continuous fabrication of such a wire starts with a core which iswound on a drum. The core traverses, under the action of driving means,apparatus comprising in succession, preparation means for such core,means for deposition of the layer, means for treatment of the magneticlayer on the core, and a device for measuring the magnetic properties ofthe fabricated wire. This arrangement is characterized in that thedriving means comprises, first, a motor driving the drum to unwind thecore to provide a zero-tension sag in the core between drum andfabrication apparatus, a device for sensing the dimensional extent ofsaid sag, and means controlled by the sag sensing device for providingregulation of the speed of the motor to a value greater or lesser inaccordance with the tendency of the size of the sag to decrease or toincrease, and, second, a driving device disposed between the fabricationapparatus and the measuring device.

Thus, the core is pulled under very low mechanical tension through themeans of deposition and of treatment, such that the two steps can becarried out under the best conditions. Furthermore, the wire is pushedthrough the measuring device so that its properties can be measuredwithout stresses, which is important because it will be employed withoutstresses. In addition, when the measuring device effects amagnetostriction test of the magnetic deposit, which necessitates amechanical torsion or a tension of the wire, the conditions ofdeposition (which are sensitive to external stresses), are not disturbedbecause the driving device is formed, for example, of two rollersturning in opposite sense between which passes the wire, therebyisolating the means of deposition and of treatment from the measuringdevice.

BRIEF DESCRIPTION OF THE DRAWING The invention will be described withreference to the accompanying drawing, wherein:

The sole figure illustrates schematically the process and thearrangement of the invention providing for obtaining continuously awire, especially adapted for magnetic memories, having a conductive corecovered with a thin magnetic sheath.

DESCRIPTION OF THE PREFERRED EMBODIMENT A conductive metallic core 1,for example a wire of an alloy of copper and of beryllium having adiameter of some 10s of microns, is unwound from a drum 2 by the actionof a roller 3 keyed on a shaft 4 of an electric motor 5.

This conductive core 1 is then introduced into a fabrication apparatus 6which provides for obtaining at its output a wire 7 having a corecovered with a thin magnetic sheath. Wire 7 is pulled in the directionof the arrow F through apparatus 6 by a device 8, which comprises thenon-slipping driving rollers 9 and 10 between which passes wire 7. Next,wire 7 is pushed through a device 11 for measuring the wire s physicalproperties and then a cutting device 12. The latter can be controlled bydevice 1 1 for cutting wire in which a defect is detected.

Conductive core 1 is disposed in a manner to have a sag of predeterminedsize between drum 2 and device 6. This sag is maintained as constant aspossible by means of a servomechanism which enables regulation of thespeed of motor 5 to a greater or lesser value according to the tendencyof the sag to decrease or to increase. This sag provides a supply of thecore of substantially zero tension for the subsequent fabrication.

This servomechanism consists of a sag sensing device comprising twocontact members 16 and 17 disposed on opposite sides of conductive core1 and connected to two inputs 36 and 37 of an electrical device 35. Theoutput terminals 38 of device 35 are connected to the supply terminalsof motor by connecting leads 15. The servomechanism is arranged so as todeliver on output terminals 38 a supply voltage V or a supply voltage U,according to whether input 36 or input 37 is placed at the potential ofconductive core 1.

These supply voltages U and V are such that conductive core 1 is unwoundfrom drum 2 with a speed which is less or greater than its velocity oftransit through device 8, according to whether the motor is supplied bythe voltage U or the voltage V.

When the sag tends to decrease, conductive core 1 makes contact withcontact member 16, input 36 of electrical device 35 is placed at thepotential of conductive core 1, and device 35 furnishes to motor 5 thesupply voltage V. The conductive core is then unwound from drum 2 at agreater speed than its velocity of transit through device 8 and the sagtends to increase.

Conversely, when the sag ends to increase, conductive core 1 makescontact with contact member 17, input 37 of electrical device 35 isplaced at the potential of conductive core 1, and device 35 furnishes tomotor 5 the supply voltage U. The conductive core is then unwound fromdrum 2 at a lesser speed than its velocity of transit through device 8and the sag tends to decrease.

Accordingly, an unwinding device is provided for unwinding the core fromits roll and feeding it to the input of fabrication apparatus 6 withsubstantially zero tension on the wire at the input point of thefabrication apparatus. Therefore, the wire can be drawn through thefabrication apparatus with the exertion of only minumum tension in thepulling device, i.e., the tension required only to overcome the residualfriction imposed on the wire as it passes through the fluid-lubricatedopening in each wall of the electrolysis and rinsing tanks. Hence, awire processed according to the instant invention is coated with amagnetic film under substantially zero imposed stresses. This is veryimportant for a high quality of finished wire.

Fabrication apparatus 6 comprises a plurality of tanks 18-28 and an oven29 traversed by the wire. These tanks and the oven, as well as drivingdevice 8, measuring device 11, and cutting device 12 are mountedslidably, but in a manner to be' able to be removable or fixed on a rail30 parallel to the wire.

The wire passes through each of devices 18-29, 8, 11, and 12. Thesurface of core 1 is first subjected to preparation in treatment means31, comprising the electrolysis tanks 18, 20, 22, and 23. In theseelectrolysis tanks core 1 serves as the cathode or the anode and issurrounded by a helicoidal or annular anode or cathode, according to theparticular circumstances. The electrolyte in tanks 18, 20, 22, and 23 ispreferably circulated. Rinsing tanks 19, 21, and 24 for the circulationof water are similarly provided in treatment means 31. Depending on thevelocity of displacement of core 1, the length of electrolysis tanks 18,20, 22, and 23 are chosen in order that each portion of the core remainsabout 1 minute in such tanks.

Core 1 is introduced into electrolysis tank 18, which contains adegreasing bath formed of a mixture of sodium bicarbonate and of sodiumcarbonate at 60 C. The current density is about 20 amperes per squaredecimeter.

After having traversed rinsing tank 19, core 1 enters into electrolysistank 20, which contains a deoxidation bath formed, for example, of ahydrochloric acid bath of one-tenth normality at ambient temperature.Core 1 is again rinsed by passage through tank 21 and then is subjectedto a polishing. To effect this, it traverses an electrolysis tank 22containing an 85 percent orthophosphoric acid bath. This bath is at thetemperature of 17 C. and the current density is selected to beapproximately 300 milliamperes per square centimeter.

After polishing, the core is activated at the time of its passagethrough electrolysis tank 23, and then it is rinsed in tank 24. Theactivation bath of tank 23 is formed, preferably, of 30 percent sulfuricacid maintained at 50 C. The action of the sulfuric acid may beaugmented by passing core 1 later into a hath (not shown) containing 30percent nitric acid held at 1 7 C.

The core emerging from treatment means 31 is at that time prepared forreceiving a conductive deposit of copper, which is provided by means 32containing, for example, two electrolysis tanks 25 and 26. in these twotanks, as well as in that hearing reference numeral 28, which will bedescribed hereinafter, the electrolyte is circulated so as to cause onlya very weak agitation.

Tanks 25 and 26 contain a copper-plating bath of 250 grams per liter ofcuprous sulfate mixed with sulfuric acid. This bath is employed at atemperature below 40 C. with a current density of some tens ofmilliamperes per square centimeter. it is thus possible to cover core 1with a copper layer of some thousands of angstroms of thickness.

In some circumstances, deposition means 32 includes a gilding device(not shown) permitting the deposit of copper to be covered with a layerof gold of some thousands of angstroms.

In the instance where it is desired to obtain a wire for a memory inwhich the information must not be destroyed by reading, the wireemerging from deposition means 32 passes through an electrolytic tank 27containing an acid solution.

After its passage through tank 27, the wire traverses an electrolysistank 28 containing a bath capable of depositing on such wire a layer ofmagnetic material. This bath may be that which is described in FrenchPat. No. 1,438,564 and which provides for the deposition on a copperwire of an alloy of iron and nickel comprising about 18 percent of iron.This ironnickel electrolyte permits obtaining suitable speeds ofdeposition without agitation and controlling almost perfectly thethickness of the deposit. Moreover, it has the advantage of giving tothe deposit zero magnetostriction (at 18 percent of iron) and very lowinternal stresses. Nevertheless, this electrolyte does not toleratelarge variations of potential along the wire without creating variationsin the composition of the magnetic deposit along tank 28 and acomposition gradient in the thickness. This disadvantage may be avoidedby adapting the procedure described in French Pat. No. 1,533 ,398.

One such alloy of iron and nickel which is known comprises voids, thatis to say crystalline gaps, which through their subsequent displacementin time modify the magnetic properties of the sheath. In order toeliminate this known property of these voids, the wire covered by itsmagnetic layer is introduced into an oven 29 which subjects the wire toannealing at a temperature of the order of 300 C., in certaincircumstances in the presence of a magnetic field.

From the output of annealing oven 29, wire 7, consisting of core 1covered with a magnetic layer passes between driving rollers 9 and 10 ofdevice 8, which pushes the wire into device 11 for measuring itsproperties, then into cutting device 12. The latter may be controlled bydevice 11 for cutting the wire when a defect is detected.

Since the core-supplying servomechanism supplies all of the force andenergy required to maintain the core at a constant mid-sag level, to thedevice 8 pulling the core through the fabrication apparatus, the corevirtually commences at the mid-bottom of the sag, and the only pullrequired of device 8 ahead of the fabrication apparatus is that requiredto lift the small length of core between the mid-bottom of the sag andthe input of the fabrication apparatus. Thus the sag becomes azero-tension reservoir of core for the processing apparatus. Device 8has only to overcome the residual friction imposed on the wire as itpasses through the fluid-lubricated openings in the wall of the tanks.

Thus, the wire is pulled through fabrication apparatus 6 and pushedthrough measuring device 11. This mode of fabrication in accordance withthe invention is, as has been explained above, particularly important.Moreover, in accordance with the invention, the position of drivingdevice 8 is between device 11 and oven 29 which stabilizes by annealing.

Core 1 traverses the various tanks, which are sealed by means of plugsof synthetic material covering the openings provided in the opposedwalls of these tanks. These plugs comprise two parts fitted oppositeeach other along surfaces at least partially plane, one of the twoopposed plane parts being provided with a channel in which is engagedthe wire.

In some embodiments the mechanical tension exercised on the wire by eachof these plugs is only of the order of 30-60 milligrams. Therefore, thetotal tension required to pull the wire through the entire fabricationapparatus is between 0.7 and 1.4 grams.

The details of the particular process which has been described above maybe modified without departing from the heart of the present invention.It is thus possible to modify the fabrication apparatus and themeasuring device without departing from the invention.

We claim:

1. An arrangement provided with fabrication apparatus for the continuousfabrication of a wire having a conductive core covered with a thinmagnetic film starting with a core which is wound on a drum and whichtraverses, under the action of driving means, said fabricationapparatus, wherein said fabrication apparatus comprises, successively,means for preparation of the core, means for electrolyticly depositingthe magnetic film on said core, and means for the treatment of amagnetic film on said core, said arrangement being provided further witha device for measuring the magnetic properties of the completed wire,wherein the improvement comprises: said driving means comprising a firstmeans having a motor driving said drum in a sense to unwind said core, adevice for sensing the sag of said core in the portion thereof betweensaid drum and said fabrication apparatus, and means controlled by saidsensing device for regulating the speed of said motor to a value greateror less in accordance with the tendency of the sag to decrease or toincrease, and a second means having a driving device disposed betweensaid fabrication apparatus and said measuring device.

2. The arrangement of claim 1, wherein said driving device comprisesrollers between which passes the wire emerging from the fabricationapparatus.

3. The arrangement of claim 1, wherein there is further provided,following the device for measuring the magnetic properties of thecompleted wire, a device for cutting the completed wire controlled bysaid measuring device.

4. Apparatus for continuously fabricating a wire having a core with alayer thereon, said core being initially provided as a roll, comprising:a deposition device for continuously electrolyticly depositing saidlayer on said core as said core passes therethrough, first driving meansfor unwinding said core from said roll and inserting it into one end ofsaid deposition device, wherein said first driving means maintains a sagin said core between said roll and said deposition device, said sagbeing maintained between predetermined maximum limits, and seconddriving means for pulling the coated core emerging from said depositiondevice with a very low tension.

5. The apparatus of claim 4, further including a testing device fortesting the condition of said layer on the core of said completed wire,wherein the second driving means pushes the completed core through atesting device.

6. The apparatus of claim 4 wherein said first driving means unwindssaid core from said roll with a speed for maintaining substantially zerotension in said core at a point between said roll and said depositiondevice.

7. Apparatus for continuously fabricating a wire having a conductivecore covered with a thin magnetic layer, comprising, in combination:deposition means for receiving said core and for electrolyticlydepositing said layer on said core as said core moves therethrough,supply means disposed at one end of said deposition means for supplyingsaid core to said deposition means with substantially zero tension insaid core, and driving means disposed at the other end of saiddeposition means for pulling the coated core emerging from saiddeposition means.

8. The apparatus of claim 7 wherein the tension exerted by said drivingmeans to pull said coated core is substantially that required forovercoming the residual friction imposed on said core in passing throughsaid deposition means.

9. The apparatus of claim 7 further including a testing device fortesting the condition of the layer on said core, and wherein saiddriving means pushes the coated core pulled from said deposition meansthrough said testing device.

10. The apparatus of claim 7 wherein said supply means comprises aservomechanism for maintaining substantially zero tension in the coresupplied to said deposition means.

11. The apparatus of claim 10 wherein said servomechanism maintains asag in said core between predetermined dimensional bounds.

STATES PATENT UFEFKCE e mmmm or eomtem Patent No. 3 669 86" Dated June13,, 1972 lnventofls) Rene Fernand Victor Girard et a1 It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 6, line 9, before "limits" insert and Signed and sealed this 19thday of December l9'Z2a Eomm MQFLETCHEFQJR ROBERT GOTTSCHALK ttestingOfficer Commissioner of Patents ORM Po-1050 (10-69) USCOMM-DC 60876-P69U.S. GOVERNMENT PRINTING OFFICE: 1969 0-366-384.

1. An arrangement provided with fabrication apparatus for the continuousfabrication of a wire having a conductive core covered with a thinmagnetic film starting with a core which is wound on a drum and whichtraverses, under the action of driving means, said fabricationapparatus, wherein said fabrication apparatus comprises, successively,means for preparation of the core, means for electrolyticly depositingthe magnetic film on said core, and means for the treatment of amagnetic film on said core, said arrangement being provided further witha device for measuring the magnetic properties of the completed wire,wherein the improvement comprises: said driving means comprising a firstmeans having a motor driving said drum in a sense to unwind said core, adevice for sensing the sag of said core in the portion thereof betweensaid drum and said fabrication apparatus, and means controlled by saidsensing device for regulating the speed of said motor to a value greateror less in accordance with the tendency of the sag to decrease or toincrease, and a second means having a driving device disposed betweensaid fabrication apparatus and said measuring device.
 2. ThE arrangementof claim 1, wherein said driving device comprises rollers between whichpasses the wire emerging from the fabrication apparatus.
 3. Thearrangement of claim 1, wherein there is further provided, following thedevice for measuring the magnetic properties of the completed wire, adevice for cutting the completed wire controlled by said measuringdevice.
 4. Apparatus for continuously fabricating a wire having a corewith a layer thereon, said core being initially provided as a roll,comprising: a deposition device for continuously electrolyticlydepositing said layer on said core as said core passes therethrough,first driving means for unwinding said core from said roll and insertingit into one end of said deposition device, wherein said first drivingmeans maintains a sag in said core between said roll and said depositiondevice, said sag being maintained between predetermined maximum limits,and second driving means for pulling the coated core emerging from saiddeposition device with a very low tension.
 5. The apparatus of claim 4,further including a testing device for testing the condition of saidlayer on the core of said completed wire, wherein the second drivingmeans pushes the completed core through a testing device.
 6. Theapparatus of claim 4 wherein said first driving means unwinds said corefrom said roll with a speed for maintaining substantially zero tensionin said core at a point between said roll and said deposition device. 7.Apparatus for continuously fabricating a wire having a conductive corecovered with a thin magnetic layer, comprising, in combination:deposition means for receiving said core and for electrolyticlydepositing said layer on said core as said core moves therethrough,supply means disposed at one end of said deposition means for supplyingsaid core to said deposition means with substantially zero tension insaid core, and driving means disposed at the other end of saiddeposition means for pulling the coated core emerging from saiddeposition means.
 8. The apparatus of claim 7 wherein the tensionexerted by said driving means to pull said coated core is substantiallythat required for overcoming the residual friction imposed on said corein passing through said deposition means.
 9. The apparatus of claim 7further including a testing device for testing the condition of thelayer on said core, and wherein said driving means pushes the coatedcore pulled from said deposition means through said testing device. 10.The apparatus of claim 7 wherein said supply means comprises aservomechanism for maintaining substantially zero tension in the coresupplied to said deposition means.
 11. The apparatus of claim 10 whereinsaid servomechanism maintains a sag in said core between predetermineddimensional bounds.